Pulmonary function tests (PFTs) are a group of tests that show how well your lungs are working. PFTs may measure:
- How much air you can blow out
- How much air your lungs can hold at different times during the breathing cycle
- How fast you are blowing air out
- How well gas is being transferred from your lungs into your blood
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Reasons for Test
PFTs may be used to help diagnose or check the affect of lung conditions or diseases, such as:
- Trouble breathing after injury to chest or surgery
- Chronic bronchitis
- Cystic fibrosis
- Alpha-1 antitrypsin deficiency
- Problems that make it hard to move air in and out of the lungs from scoliosis, tumors, inflammation, or scarring of the lungs
- Idiopathic pulmonary fibrosis
- Interstitial lung disease
These tests may also be done to:
- Show how well a treatment is working
- Check affect of symptoms, such as coughing, wheezing, and trouble breathing
- Check how well your lungs are working before or after a surgery
- Measure a lung problem or muscle weakness
There are no major problems linked to these tests.
What to Expect
Prior to Test
- Review your medicine with your doctor. You may need to stop taking some before testing.
- Do not eat, smoke, or exercise for 4 to 8 hours before testing.
- Wear loose-fitting clothing.
Description of Test
The exact steps will depend on the reason for the test. In most cases, the procedure will be as follows:
- You will be asked to loosen tight clothing, or jewelry. You will need to wear dentures if you have them.
- You will sit in a chair. A soft clip will be put on your nose. All of your breathing will need to pass through your mouth.
- The doctor will ask you to breathe into a mouthpiece. The mouthpiece is attached to a tool that measure breath.
- You will be asked to breathe in and out in different ways.
- The team will watch you carefully for dizziness, trouble breathing, or other problems.
You may be given medicine to inhale after certain tests. The tests will then be repeated after the medicine has started to work.
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Other steps that may be needed include:
- A brief period of exercise before the test.
- A small clip will be attached to your finger. It will measure the amount of oxygen in your blood.
- A special chemical will be given as a mist. If you have asthma the chemical will cause a spasm in the airway. This is only done under medical care.
- You may be asked to breathe in small amount of carbon monoxide for 1 minute. It will be followed to see how much gets into your blood. This will show how well oxygen is getting into your blood.
Rest until you feel able to leave. You may have wheezing, coughing, and/or problems breathing. It will be treated before you leave.
How Long Will It Take?
20 to 45 minutes
Will It Hurt?
The test does not hurt. You may feel some symptoms during or right after testing.
Your doctor will compare the results of your tests with normal values. The results will also be checked with tests you may have already done. Your doctor will discuss the results with you.
Call Your Doctor
After the test, call your doctor if any of the following occurs:
- Headaches, nausea, muscle aches, lightheadedness, or general ill feeling
- Shortness of breath or difficulty breathing
- Wheezing or persistent coughing
- Chest pain
American Lung Association
Family Doctor—American Academy of Family Physicians
Pulmonary function tests. EBSCO DynaMed Plus website. Available at:http://www.dynamed.com/topics/dmp~AN~T900274/Pulmonary-function-tests. Updated March 20, 2019. Accessed December 17, 2019.
Pulmonary Disease, Chronic Obstructive (COPD): Quality of Life. EBSCO Nursing Reference Center website. Available at: http://www.ebscohost.com/nursing/products/nursing-reference-center. Updated December 28, 2018. Accessed December 17, 2019.
Last reviewed December 2019 by EBSCO Medical Review Board Nicole Meregian, PA Last Updated: 8/7/2020